1. Field of the Invention
The invention relates generally to trailer construction and in particular to a pneumatic lift system for a single axle utility trailer.
2. Description of the Prior Art
Single axle trailers are widely used to transport heavy loads. For example the single axle trailer is commonly used to transport mobile homes, do-it-yourself moving vans, and boats. In the construction industry, the single axle trailer is used to transport heavy equipment such as portable power plants, welding rigs, and air compressors. In the usual arrangement, the single axle trailer includes a tongue and a hitching member such as a hitching eye or hitching cup for engagement with a coupling member of a tow truck. The tongue of a small, relatively light trailer can be lifted for attachment to a tow truck by a single operator. However, for larger trailer assemblies, and especially those which are loaded, the weight of the trailer tongue may be more than a single operator can safely handle.
In the construction of single axle trailers which are designed to carry very heavy loads, for example an air compressor trailer assembly which may have a gross weight of 2500 pounds or more, the load is distributed along the longitudinal axis of the trailer so that its center of gravity is shifted forward of the axle in the direction of travel to minimize the "fishtailing" effect as the trailer is towed. In a typical arrangement, the tongue is loaded by approximately ten percent of the gross weight. Attempts by a single operator to lift this load have resulted in back, foot and hand injuries.
Various mechanical hand operated jacks have been successfully used for performing the lifting operation relatively safely. However, because it is necessary to align the hitching member fairly precisely in the lateral direction as well as in the vertical direction with respect to the coupling member of the tow truck, the use of the hand-powered mechanical jack is relatively awkward since lateral positioning cannot be coordinated with the vertical positioning without risk of upsetting the jack.